Silver halide grains precipitated in the presence of a phosphoric acid amide sensitizer

ABSTRACT

The light-sensitivity of a photographic material comprising at least one supported silver salt emulsion layer is improved by the addition of a water-soluble phosphoric acid amide as defined below.

United States Patent 1 Saleck et al.

[ Nov. 26, 1974 1 SILVER HALIDE GRAINS PRECIPITATED IN THE PRESENCE OF A PHOSPHORIC ACID AMIDE SENSITIZER [75] Inventors: Wilhelm Saleck, Schildgen;

Wolfgang Himmelmann, Opladen; Gerhard Balle; Karl-Erwin Schnalke, both of Koeln, all of Germany [73] Assignee: Agfa-Gevaert Aktiengesellschaft,

Leverkusen, Germany 22 Filed: Nov. 29, 1972 21 Appl. No.: 310,635

[30] Foreign Application Priority Data Dec. 4, 1971 Germany 2160207 [52] US. Cl. 96/107, 96/109 Primary E.raminerDavid Klein Assistant ExaminerWon H. Louie, Jr. Attorney, Agent, or Firm-C0nnolly and Hutz [57] ABSTRACT The light-sensitivity of a photographic material comprising at least one supported silver salt emulsion layer is improved by the addition of a water-soluble phosphoric acid amide as defined below.

2 Claims, No Drawings Mackey et al. 96/107 This invention relates to a photographic silver salt emulsion with increased sensitivity which is achieved by the addition of phosphoric acid amides.

The sensitivity to light'of a photographic silver salt emulsion can be influenced in two ways. Firstly, it can be increased by suitable choice of the precipitation conditions and of the so-called physical ripening. In practice, the possibility of increasing the sensitivity in this way is limited by the fact that the increase in sensitivity is accompanied by an increase of the grain size, which deleteriously effects the quality of the final image. lt is therefore desired to obtain silver salt emulsions with a very high light-sensitivity but fine grain.

Secondly, the sensitivity of photographic emulsions can be increased by chemical methods by adding compounds which are generally known as chemical sensitizers. In principle, these compounds could be added at any stage of the preparation of the emulsion, e.g., as ripening additives before chemical ripening or to the finished casting solution after chemical ripening. Ripening agents are e.g., noble metal salts, particularly gold salts, and sulfur compounds such as thiosulfates or organic and particularly heterocyclic sulfur compounds. A disadvantage of the chemical sensitization method is that the increase in sensitivity is accompanied by an increased tendency of the emulsion to form an uniform fog which is capable of being developed. For this reason, very active chemical sensitizers such as compounds with an onium structure, e.g., quaternary ammonium or phosphonium salts or ternary sulfonium salts or polyalkylene oxides and polyalkylene oxide de' rivatives can only be added to the finished casting solution after chemical ripening. If such substances were added before chemical ripening, the photographic silver salt emulsions would be so heavily fogged that they would be practically useless.

None of the known chemical sensitizers adequately satisfies practical requirements, either because the increase in sensitivity achieved is insufficient or because concomitant fogging prevents application of the sensitizer.

lt is among objects of the present invention to provide new chemical sensitizers which do not have the above disadvantages and which increase the lightsensitivity of photographic silver salt emulsions, and particularly of photographic silver halide emulsions without unwanted fogging.

We now have found a photographic material containing at least one silver salt emulsion layer which contains, as chemical sensitizer, a water-soluble 'phosphoric acid amide of the following formula:

I ii/ n sog in which v R (l) a saturated or olefinically unsaturated aliphatic group, preferably alkyl, in particular alkyl having one to three carbon atoms, (2) aryl, in particular phenyl, which may be substituted, e.g,, with alkyl or alkoxy, both of which preferably have up to three carbon atoms, or with carboxyl, sulfo, sulfonamido, alkyl, sulfonyl, halogen such as fluorine, chlorine orbromine, or nitrile, or (3) cycloalkyl such as cyclopentyl or cyclohexyl;

R 1) hydrogen, (2) a saturated or olefinically unsaturated aliphatic group, preferably alkyl, in particular alkyl with one to three carbon atoms, (3) aryl, in particular phenyl, which may be substituted, e.g., with alkylor alkoxy, both of which preferably have up to three carbon atoms, or with carboxyl, sulfo, sulfonamido, alkyl sulfonyl, halogen such as fluorine, chlorine or bromine or nitrile, or (4) cycloalkyl such as cyclopentyl or cyclohexyl; halogen, particularly chlorine, or hydroxyl and X halogen, in particular chlorine, or hydroxyl or an amino group which may be substituted with a saturated or olefinically unsaturated aliphatic group having preferably up to three carbon atoms, aryl, particularly phenyl, or cycloalkyl such as cyclopentyl or cyclohexyl.

The following are examples of suitable compounds:

- ll s O2NHP(CI)2 Methods of preparing the compounds used according to the invention are known. Reference may be made to the following publications:

Houben-Weyl XII/2 (1964), pages 525 et seq.;

A. V. Kirsanov, lzv. Akad. SSSR, 1952, 710

A. V. Kirsanov and E. A. Abrazhanova, Sbornik Sta- I tei Obshchei Khim. Z. 1048 (1953).

The preparation of two of the compoundsis described in detail below. Compound 1 Phosphoric acid (N-phenylsulfonylamide)-dichloride 0.01 mol of phosphoric acid phenylsulfonyliminotrichloride in 50 ml of anhydrous benzene and 0.01 mol of anhydrous formic acid are stirred together. Carbon monoxide and hydrogen chloride start to evolve after a short time. Stirring is continued until no furtherevolution of gas can be observed. The reaction product which precipitates is suction-filtered and recrystallized from carbon tetrachloride or petroleum ether. Compound 2 Phosphoric acid mono-(phenylsulfonyl-amide) 0.01 mol of phosphoric acid (N-phenylsulfonylamide)-dichloride and 0.02 mol of anhydrous formic acid in 50 ml of anhydrous benzene or dioxane are heated together at 80 100C for 12 hours and the precipitated reaction product is suction filtered and washed with benzene.

The photographic silver salt emulsions chemically sensitized in accordance with the invention are prepared by the usual methods. The method of preparation comprises the following steps:

1. Precipitation of the silver salts, in particular silver halides, in the presence of a protective colloid and physical ripening;

2. coagulation and flocculation of the emulsion and removal. by washing, of the water-soluble silver salts formed at the precipitation stage and 3. redispersion of the washed emulsion and chemical ripening.

The chemical sensitizer of the present invention are added to the photographic silver salt emulsion before chemical ripening, preferably at the precipitation stage. The quantity to be added depends on the desired effect and can be determined by a few simple tests in the usual manner. Quantities of from 1 to 50 g. based on 100 g of gelatin. are generally sufficient. Based on the quantity of silver halide to be precipitated. the quantities to be used are 150 mg 8 g, preferably 300 mg 4 g, per mol of silver halide.

The substances to be used according to the invention are preferably added in the form of their aqueous solutions. The concentration of substances in these solutions is not critical and may vary within wide limits. The phosphoric acid amides should be water-soluble to the extent that it is possible to prepare an aqueous solution which contains a sufficient quantity of active substance. It is sufficient, for example, to prepare a 1 5 percent solution. If the substances are particularly easily soluble the solutions may, of course, be more concentrated. The solutions are generally prepared at a pH of about 7 but the pH may also be kept slightly acid, e.g., between 5 and 7, or in the case of so-called ammoniacal emulsions the pH of the solution may be between -5 and 9.

lulosefpolyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts, esters or amides or proteins, preferably gelatin. s

The emulsions may also contain other chemical sensitizers, e.g., quaternary ammonium and phosphonium salts or ternary sulfonium salts, reducing agents such as tin-(ll) salts, polyamines such as diethylenetriamine or sulfur compounds as described in US. Pat. No. 1,574,944. The emulsions may also contain salts of noble metals such as ruthenium, rhodium, palladium, iridium, platinum or gold as chemical sensitizers as described in the article by R. KOSLOWSKY, Z. Wis- -s.Phot. 46, 72 1951 They may also contain polyalkylene oxides or polyalkylene oxide derivatives as development accelerators or chemical sensitizers. An additional increase in sensitivity is thereby achieved.

The emulsions may also be optically sensitized, e.g., with the usual polymethine dyes such as neutrocyanine,

. basic or acid carbocyanines, rhodacyanines, hemicyanines, styryl dyes and oxonoles. Sensitizers of this kind have been described by F. M. HAMER in The Cyanine Dyes and related Compounds, lnterscience Publishers, a division of John Wiley and Sons, New York (1964).

The emulsions may contain the usual stabilizers, e.g., homopolar or salt-type compounds of mercury containing aromatic or heterocyclic rings (for example mercaptotriazoles), simple mercury salts, sulfonium mercury double salts and other mercury compounds.

Azaindenes are also suitable stabilizers. especially tetraor penta-azaindenes, particularly those which are substituted with hydroxyl or amino groups. Compounds of this kind have been described in the article by BlRR, Z.Wiss.Phot. 47, 2 58 (1952). Other suitable stabilizers include heterocyclic mercapto compounds, e.g. phenyl mercaptotetrazole, quaternary benzothiazole derivatives and benzotriazole.

The emulsions may be hardened in the usual manner, for example with formaldehyde or halogenated aldehydes which contain a carboxyl group, such as mucobromic acid, diketones, methane sulfonic acid esters and dialdehydes or polyfunctional triazine derivatives such as tri-acryloyl-hexahydrotriazine or halogenated or alkoxy-substituted hexahydrotriazine derivatives.

The substances according to the invention produce their advantageous effect not only in black and white emulsions but also in the production of color photographic images. They are readily compatible with the usual color couplers. The phosphoric acid amides may also be used with direct positive emulsions, e.g., those which have a composite grain structure in accordance with French Pat. No. 1,585,791. They are also suitable for emulsions used for the silver dye bleaching process or dye diffusion process.

A particularly advantageous effect is achieved with phosphoric acid amides in those silver salt emulsions which are precipitated in the presence of silica sols. The preparation of such emulsions has been described in US. Pat. No. 3,637,391.

According to another preferred embodiment of the invention, the phosphoric acid amides are used in combination with polymers which contain disulfonimide groups. Such compounds have been described in German Pat. No. 1,089,548 and in U.S. Pat. No.

3,052,656. The polymeric disulfonimides are added be-.

fore chemical ripening, in particular at the precipitation or'flocculation stage. The concentration of the disulfonimides may vary within wide limits. Quantities of l to percent, based on the gelatin originally put into the process, have generally been found to be sufficient.

' sulfuric acid. The flocculate is left to settle and the supernatant solution is drawn off. The flocculate is then twice washed with litres of water in which it is agitated by stirring for 5 minutes. After the final removal of supernatant water, the flocculate is dissolved in the appropriate quantity of water; gelatin at pH 7 at C,. gold-(Ill) chloride and sodium thiosulfate are added as ripening additives and, after adjustment of the pAg to 8.9, the emulsion is ripened at a ripening temperature of 48C.

Sample 2 The emulsion is prepared in the same way as in sample l above but during precipitation, ml of a 7 percent aqueous solution of compound] are added to the given gelatin/alkali metal halide solution.

Samples 3 9 are prepared accordingly by the addition of the same amount of compounds 2 5 and 7 9.

The samples are cast on a cellulose acetate support after the addition, per kg of emulsion, of 10 ml, of a 5 percent aqueous solution of saponin as wetting agent, 10 ml of a 10 percent aqueous solution of formaldehyde as hardener and 20 ml of a 1 percent methanolic solution of 4-hydroxy-6-methyl-l,3,3a,7- tetraazaindene as stabilizer. After exposure in a conventional sensitometer behind a step wedge and development (7 and 16 minutes at 20) in a developer of the following composition Sodium sult'ile sicc. Borax 7 Hydroquinone 3.. p-monomethylaminophenol sulfate 3 Sodium citrate 7. Potassium bromide 0. made up to 1 litre with water the emulsions are assessed sensitometrically. From the following table it will be seen that emulsions 2 9 have a higher sensitivity than comparison emulsion l.

Table Sample 7 minutes development 16 minutes development Sensiy Fog Sensi 'y Fog tivity tivity 1 Standard 0.60 0.16 Standard 0.90 0.21 2 l.5 0.65 0.18 1 0,85 0.25 3 1 0.60 0.15 0.5 0.80 0.18 4 l.5 0.70 0.14 1 0.95 0.16 5 15 0.65 0.16 1 0.85 0.19 6 +1 0.60 0.13 1 0.75 0.16 7 1 0.65 0.15 +1 080 0.17 8 0.5 0.60 0.12 1 0.70 0.15 9 l.5 0.75 0.15 l 0.95 0.20

3 l shutter stop We claim:

1. A process for the preparation of photographic silver halide emulsions comprising the steps of precipitating the silver halide in a gelatin emulsion, physically ripening, flocculating and solidifying the precipitated silver halide emulsion, and then chemically ripening the emulsion, including adding a sensitizer from the group consisting of noble metal salts and sulfur compounds after the solidifying step wherein the improvement comprises in the preparation of the emulsion adding to the gelatin emulsion during precipitation of silver halide a phosphoric acid amide to sensitize the emulsion said amide is of the following formula:

in which R is (l) a saturated or olefinically unsaturated alkyl group, (2) phenyl, (3) cyclopentyl or cyclohexyl;

R represents (1) hydrogen, (2) a saturated or olefinically unsaturated alkyl group, (3) phenyl or (4) cyclopentyl or cyclohexyl;

X stands for halogen or unsubstituted hydroxyl;

X represents halogen, unsubstituted hydroxyl or an unsubstituted amino group, said amide being added in an amount in the range of mg 8 g per mol of silver halide and then chemically ripening the emulsion in the presence of said phosphoric acid amide.

2. The process of claim 1, wherein R is phenyl. 

1. A PROCESS FOR THE PREPATION OF PHOTOGRAPHIC SILVER HALIDE EMULSIONS COMPRISING THE STEPS OF PRECIPITATING THE SILVER HALIDE IN A GELATIN EMULSION, PHYSICALLY RIPENING, FLOCCULATING AND SOLIDIFYING THE PRECIPITATED SILVER HALIDE EMULSION, AND THEN CHEMICALLY RIPENING THE EMULSION, INCLUDING ADDING A SENSITIZER FROM THE GROUP CONSISTING OF NOBLE METAL SALTS OF SULFUR COMPOUNDS AFTER THE SOLIDIFYING STEP WHEREI N THE IMPROVEMENT COMPRISES IN THE PREPARATION OF THE EMULSION ADDING TO THE GELATIN EMULSION DURING PRECIPITATION OF SILVER HALIDE A PHOSPHORIC ACID AMIDE TO SENSITIZE THE EMULSION SAID AMIDE IS OF THE FOLLOWING FORMULA:
 2. The process of claim 1, wherein R1 is phenyl. 